Cell Surface Display, Screening and Production of Proteins of Interest

Abstract

Aspects of the invention provide compositions and methods for displaying engineered polypeptides on a cell surface. According to aspects of the invention, immobilized polypeptides can be screened to identify one or more variants having one or more functional or structural properties of interest. Aspects of the invention provide composition and methods for producing engineered protein or protein variants having a functional or a structural property of interest.

1 . A protein screening method comprising:
 a. expressing an engineered protein comprising a modification motif in a host cell having a cell surface comprising a first binding partner, wherein a second binding partner is coupled to the expressed engineered protein, and wherein the expressed engineered protein is secreted and displayed on the cell surface via binding of the second binding partner to the first binding partner; and,   b. evaluating a property of the engineered protein displayed on the cell surface.   
     
     
         2 . The method of  claim 1 , wherein the evaluating step comprises assaying a level of activity, determining whether the engineered protein has a predetermined function, comparing the property of the engineered protein to the property of a reference protein, determining the amount of the engineered protein displayed on the cell surface, or any combination thereof. 
     
     
         3 . The method of  claim 1 , wherein the engineered protein is an antibody, a single chain antibody, a scaffold protein, or a fragment thereof, and the function of the protein being evaluated is the binding affinity of the protein to the target molecule, wherein the target molecule comprises an antigen and/or epitope. 
     
     
         4 . The method of  claim 1 , wherein host cells are selected on the basis of a first predetermined property of the displayed engineered protein. 
     
     
         5 . The method of  claim 4 , further comprising selecting the host cells on the basis of a second predetermined property of the displayed engineered protein. 
     
     
         6 . The method of  claim 4 , further comprising releasing the engineered protein from selected host cells displaying at least the predetermined level of the engineered protein. 
     
     
         7 . The method of  claim 2 , wherein assaying a level of activity comprises assaying if the engineered protein can process a substrate. 
     
     
         8 . The method of  claim 7 , wherein the substrate is coupled to the surface. 
     
     
         9 . The method of  claim 7 , wherein the substrate is a polypeptide, nucleic acid, lipid, polysaccharide, synthetic polymer or synthetic compound. 
     
     
         10 . The method of  claim 7 , wherein processing a substrate comprises binding to the substrate, dissociating the substrate, nicking the substrate, cutting the substrate, activating the substrate, deactivating the substrate, charging the substrate, decharging the substrate, changing substrate conformation, copying the substrate, replicating the substrate, conjugating molecules to the substrate, conjugating peptides to the substrate or modifying the substrate. 
     
     
         11 . The method of  claim 2 , further comprising isolating an engineered protein having a predetermined function. 
     
     
         12 . The method of  claim 2 , further comprising isolating an engineered protein having a predetermined level of activity.